The present invention relates to a Fresnel LED lens and a LED assembly thereof, especially to a Fresnel LED lens with a plurality of Fresnel optical surfaces that is arranged linearly, and it can be assembled with other components to form a light source to apply to illumination, flashlights of mobile phones or cameras.
LED with features of low voltage, low power consumption and long operation life has been broadly applied to indicators, illuminators and so on. Compared with conventional light sources, light emitted from the LED chip is scattered. Thus optical lenses are required to concentrate light in small area or to uniformize light in large area. In lens design of LED, there are two lens types—primary optical lens and secondary optical lens. The primary optical lens is a lens directly packaged on the LED chip and it is used for concentrating light. The secondary optical lens is an LED array formed by signal chip or a plurality of LED chips, and it is used for spreading or unifying light beams. As to the design of the secondary optical lens, Fresnel lens is used so as to reduce thickness of the secondary optical lens. The Fresnel lens with a single LED is shown in FIG. 1 and FIG. 2, light is emitted from a LED 21, concentrated by a Fresnel lens 23, and projected onto a target, as revealed in JP 2005257953, Taiwan Pat. No. M347533, M347534 and U.S. Pat. No. 6,726,859. The Fresnel lens with a LED array is shown in FIG. 3 and FIG. 4, as revealed in US2007/0275344, US2008/0158854, US2002/0025157, US2007/0034890, EP1091167 etc.
In order to meet requirements of power saving and compact design, LED is applied to flashlights of digital still cameras, PC cameras, network cameras, mobile phones etc. The LED lights or flashlight applied to such products are formed by a single LED or a LED array having a plurality of LED. Then a secondary optical lens is added so as to enable illumination and light intensity as uniform as possible. The light distribution pattern requires uniform light intensity and quasi-circle distribution pattern is most suitable to be applied to lighting or flashlights. The Fresnel-type secondary optical lens makes light emitted from LED achieve maximum efficiency. Thus there is a need to provide a secondary optical lens formed by a Fresnel lens that generates quasi-circle distribution pattern and a LED assembly thereof to apply to lighting, mobile flashlights or camera flashlights.